Encoder device, drive device, stage device, and robot device

ABSTRACT

An encoder device including a position detection unit for detecting position information of a moving part; a magnet having a plurality of polarities along a moving direction of the moving part; and an electric signal generation unit for generating an electric signal, based on a magnetic characteristic of a magnetosensitive part, the electric signal generation unit having the magnetosensitive part whose magnetic characteristic is changed by a change in magnetic field associated with relative movement to the magnet, wherein the magnetosensitive part is disposed so that the magnetosensitive part is spaced apart from a side surface of the magnet in a direction orthogonal to the moving direction and a length direction of the magnetosensitive part is orthogonal to tangential directions of at least some of magnetic field lines of the magnet.

The contents of the following Japanese patent application areincorporated herein by reference:

NO. 2018-004239 filed in JP on Jan. 15, 2018, and

NO. PCT/JP2019/000306 filed in WO on Jan. 9, 2019.

BACKGROUND 1. Technical Field

The present invention relates to an encoder device, a drive device, astage device, and a robot device.

2. Related Art

An encoder device that detects position information of an object to bedetected, such as a rotating angle, a rotating speed and the like ismounted to a variety of devices such as a robot device. As the encoderdevice of the related art, known is a device that converts a change inmagnetic field of a rotating magnet into an electric signal by using amagnetic wire such as a Wiegand wire and obtains a rotating speed byusing the electric signal (for example, see Patent Document 1).

For the encoder device in which the magnetic wire is used as describedabove, it is needed to generate a stable electric signal by reducingnoises due to an unnecessary magnetic field of the magnet, therebyimproving reliability of a detection result.

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. H08-136558

GENERAL DISCLOSURE

According to a first aspect, there is provided an encoder devicecomprising a position detection unit for detecting position informationof a moving part; a magnet having a plurality of polarities along amoving direction of the moving part; and an electric signal generationunit for generating an electric signal, based on a magneticcharacteristic of a magnetosensitive part, the electric signalgeneration unit having the magnetosensitive part whose magneticcharacteristic is changed by a change in magnetic field associated withrelative movement to the magnet, wherein the magnetosensitive part isdisposed so that the magnetosensitive part is spaced apart from a sidesurface of the magnet in a direction orthogonal to the moving directionand a length direction of the magnetosensitive part is orthogonal totangential directions of at least some of magnetic field lines of themagnet.

According to a second aspect, there is provided a drive devicecomprising the encoder device according to the first aspect, and a powersupplying unit for supplying power to the moving part. According to athird aspect, there is provided a stage device comprising a movingobject, and the drive device according to the second aspect for movingthe moving object. According to a fourth aspect, there is provided arobot device comprising the drive device according to the second aspect,and an arm for causing relative movement by the drive device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an encoder device in accordance with a first embodiment.

FIG. 2A is a perspective view showing a magnet, an electric signalgeneration unit, and a magnetic sensor in FIG. 1 .

FIG. 2B is a plan view showing the magnet and the like in FIG. 2A.

FIG. 2C is a circuit diagram showing the magnetic sensor in FIG. 2A.

FIG. 3A is a plan view showing the magnet and the electric signalgeneration unit in FIG. 2A.

FIG. 3B is a sectional view of FIG. 3A.

FIG. 3C is a sectional view of FIG. 3A.

FIG. 3D is a plan view showing a modified embodiment.

FIG. 3E is a side view of FIG. 3D.

FIG. 4 shows a configuration of an electric power supplying system and amulti-turn information detection unit of the encoder device shown inFIG. 1 .

FIG. 5 shows operations of the encoder device shown in FIG. 1 duringforward rotation.

FIG. 6A is a plan view showing a magnet and an electric signalgeneration unit in accordance with a second embodiment

FIG. 6B is a side view of FIG. 6A.

FIG. 6C is an enlarged view showing a part of the magnet shown in FIG.6A.

FIG. 6D is a plan view showing a modified embodiment.

FIG. 6E is a side view of FIG. 6D.

FIG. 7A is a plan view showing a magnet and an electric signalgeneration unit in accordance with a third embodiment.

FIG. 7B is a sectional view of FIG. 7A.

FIG. 7C is a plan view showing a modified embodiment.

FIG. 8A is a plan view showing a magnet and an electric signalgeneration unit in accordance with a fourth embodiment

FIG. 8B is a sectional views of FIG. 8A.

FIG. 8C is a sectional views of FIG. 8A.

FIG. 8D is a plan view showing a modified embodiment.

FIG. 8E is a side view of FIG. 8D.

FIG. 9A is a plan view showing a magnet, an electric signal generationunit, and a magnetic sensor in accordance with a fifth embodiment.

FIG. 9B is a sectional view of FIG. 9A.

FIG. 10A is a plan view showing an electric signal generation unit, amagnetic sensor and an optical sensor in accordance with a sixthembodiment.

FIG. 10B is a sectional view of FIG. 10A.

FIG. 11 shows an example of a drive device.

FIG. 12 shows an example of a stage device.

FIG. 13 shows an example of a robot device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A first embodiment is described with reference to FIGS. 1 to 5 . FIG. 1shows an encoder device EC in accordance with the present embodiment. InFIG. 1 , the encoder device EC detects rotational position informationof a rotary shaft SF (moving part) of a motor M (power supplying unit).The rotary shaft SF is, for example, a shaft (rotor) of the motor M, butmay also be an operation shaft (output shaft) connected to the shaft ofthe motor M via a power transmission unit such as a transmission andalso connected to a load. The rotational position information detectedby the encoder device EC is supplied to a motor control unit MC. Themotor control unit MC controls rotation (for example, a rotationalposition, a rotating speed and the like) of the motor M by using therotational position information supplied from the encoder device EC. Themotor control unit MC controls the rotation of the rotary shaft SF.

The encoder device EC comprises a position detection system (positiondetection unit) 1 and an electric power supplying system (electric powersupplying unit) 2. The position detection system 1 detects therotational position information of the rotary shaft SF. The encoderdevice EC is a so-called multi-turn absolute encoder, and detects therotational position information including multi-turn informationindicative of the number of rotations of the rotary shaft SF and angularposition information indicative of an angular position (rotating angle)less than one-turn. The encoder device EC comprises a multi-turninformation detection unit 3 that detects the multi-turn information ofthe rotary shaft SF, and an angle detection unit 4 that detects theangular position of the rotary shaft SF.

At least a part (for example, the angle detection unit 4) of theposition detection system 1 operates by receiving electric power supplyfrom a device (for example, a drive device, a stage device, a robotdevice) on which the encoder device EC is mounted, in a state where apower supply (for example, a main power supply) of the device is on, forexample. Also, at least a part (for example, the multi-turn informationdetection unit 3) of the position detection system 1 operates byreceiving electric power supply from the electric power supplying system2, in a state (for example, an emergency state and a backup state) wherea power supply (for example, a main power supply) of a device on whichthe encoder device EC is mounted is off. For example, in a state wherethe supply of electric power from a device on which the encoder deviceEC is mounted is cut off, the electric power supplying system 2intermittently supplies electric power to at least a part (for example,the multi-turn information detection unit 3) of the position detectionsystem 1, and the position detection system 1 detects at least a part(for example, the multi-turn information) of the rotational positioninformation of the rotary shaft SF at the time when electric power issupplied from the electric power supplying system 2.

The multi-turn information detection unit 3 detects the multi-turninformation by magnetism, for example. The multi-turn informationdetection unit 3 includes, for example, a magnet 11, magnetism detectionunits 12, a detection unit 13, and a storage unit 14. The magnet 11 isprovided on a disc 15 fixed to the rotary shaft SF. Since the disc 15rotates together with the rotary shaft SF, the magnet 11 rotates inconjunction with the rotary shaft SF. The magnet 11 is fixed to theoutside of the rotary shaft SF, and mutual relative positions of themagnet 11 and the magnetism detection units 12 are changed due to therotation of the rotary shaft SF. The strength and direction of amagnetic field on the magnetism detection unit 12 formed by the magnet11 are changed by the rotation of the rotary shaft SF. The magnetismdetection unit 12 detects a magnetic field that is formed by the magnet,and the detection unit 13 detects the position information of the rotaryshaft SF, based on a detection result of the magnetism detection unit 12detecting the magnetic field that is formed by the magnet 11. Thestorage unit 14 stores the position information detected by thedetection unit 13.

The angle detection unit 4 is an optic or magnetic encoder, and detectsposition information (angular position information) within one-turn of ascale. For example, in a case of the optic encoder, the optic encoderdetects the angular position within one-turn of the rotary shaft SF byreading patterning information of the scale with a light-receivingelement, for example. The patterning information of the scale is, forexample, bright and dark slits on the scale. The angle detection unit 4detects the angular position information of the rotary shaft SF that isthe same as a detection target of the multi-turn information detectionunit 3. The angle detection unit 4 includes a light-emitting element 21,a scale S, a light-receiving sensor 22, and a detection unit 23.

The scale S is provided on a disc 5 fixed to the rotary shaft SF. Thescale S includes an incremental scale and an absolute scale. The scale Smay also be provided on the disc 15 or may be a member integrated withthe disc 15. For example, the scale S may be provided on an oppositesurface of the disc 15 to the magnet 11. The scale S may be provided onat least one of the inside and the outside of the magnet 11.

The light-emitting element 21 (an irradiation unit, a light-emittingunit) irradiates the scale S with light. The light-receiving sensor 22(a light detection unit) detects light emitted from the light-emittingelement 21 and passing through the scale S. In FIG. 1 , the angledetection unit 4 is a transmission type, and the light-receiving sensor22 detects light having passed through the scale S. Note that the angledetection unit 4 may also be a reflection type. The light-receivingsensor 22 supplies a signal indicative of a detection result to thedetection unit 23. The detection unit 23 detects the angular position ofthe rotary shaft SF by using the detection result of the light-receivingsensor 22. For example, the detection unit 23 detects an angularposition of a first resolution by using a detection result of light fromthe absolute scale. Also, the detection unit 23 detects an angularposition of a second resolution higher than the first resolution byperforming interpolation calculation on the angular position of thefirst resolution by using a detection result of light from theincremental scale.

In the present embodiment, the encoder device EC comprises a signalprocessing unit 25. The signal processing unit 25 calculates andprocesses a detection result of the position detection system 1. Thesignal processing unit 25 includes a synthesis unit 26 and an externalcommunication unit 27. The synthesis unit 26 acquires the angularposition information of the second resolution detected by the detectionunit 23. Also, the synthesis unit 26 acquires the multi-turn informationof the rotary shaft SF from the storage unit 14 of the multi-turninformation detection unit 3. The synthesis unit 26 synthesizes theangular position information from the detection unit 23 and themulti-turn information from the multi-turn information detection unit 3,and calculates the rotational position information. For example, whenthe detection result of the detection unit 23 is (Arad) and thedetection result of the multi-turn information detection unit 3 isn-turn, the synthesis unit 26 calculates (2π×n+θ)(rad), as therotational position information. The rotational position information mayalso be information in which the multi-turn information and the angularposition information less than one-turn are combined.

The synthesis unit 26 supplies the rotational position information tothe external communication unit 27. The external communication unit 27is communicatively connected to a communication unit MCC of the motorcontrol unit MC in a wired or wireless manner. The externalcommunication unit 27 supplies the rotational position information of adigital format to the communication unit MCC of the motor control unitMC. The motor control unit MC appropriately decodes the rotationalposition information from the external communication unit 27 of theangle detection unit 4. The motor control unit MC controls the rotationof the motor M by controlling electric power (drive electric power)supplied to the motor M by using the rotational position information.

The electric power supplying system 2 includes first and second electricsignal generation units 31A and 31B, a battery 32, and a switching unit33. The electric signal generation units 31A and 31B each generate anelectric signal by the rotation of the rotary shaft SF. The electricsignal includes a waveform where electric power (current, voltage)changes over time, for example. The electric signal generation units 31Aand 31B each generate electric power as the electric signal by amagnetic field that changes based on the rotation of the rotary shaftSF, for example. For example, the electric signal generation units 31Aand 31B generate electric power by a change in magnetic field that isformed by the magnet 11 that is used for the multi-turn informationdetection unit 3 to detect the multi-turn position of the rotary shaftSF. The electric signal generation units 31A and 31B are each disposedso that a relative angular position to the magnet 11 is changed by therotation of the rotary shaft SF. The electric signal generation units31A and 31B generate a pulsed electric signal when relative positions ofthe electric signal generation units 31A and 31B and the magnet 11 eachreach predetermined positions, for example.

The battery 32 supplies at least a part of electric power that isconsumed in the position detection system 1, based on the electricsignals generated from the electric signal generation units 31A and 31B.The battery 32 includes, for example, a primary battery 36 such as abutton-shaped battery and a dry-cell battery, and a rechargeablesecondary battery 37 (see FIG. 4 ). The secondary battery of the battery32 can be recharged by the electric signals (for example, current)generated from the electric signal generation units 31A and 31B, forexample. The battery 32 is held in a holder 35. The holder 35 is, forexample, a circuit substrate or the like on which at least a part of theposition detection system 1 is provided. The holder 35 holds thedetection unit 13, the switching unit 33, and the storage unit 14, forexample. The holder 35 is provided with a plurality of battery casescapable of accommodating the battery 32, and an electrode, a wire andthe like connected to the battery 32, for example.

The switching unit 33 switches whether to supply electric power from thebattery 32 to the position detection system 1, based on the electricsignals generated from the electric signal generation units 31A and 31B.For example, the switching unit 33 starts supply of electric power fromthe battery 32 to the position detection system 1 when levels of theelectric signals generated from the electric signal generation units 31Aand 31B become equal to or higher than a threshold value. For example,the switching unit 33 starts supplying electric power from the battery32 to the position detection system 1 when electric power equal to orhigher than the threshold value is generated from the electric signalgeneration units 31A and 31B. Also, the switching unit 33 stopssupplying electric power from the battery 32 to the position detectionsystem 1 when the levels of the electric signals generated from theelectric signal generation units 31A and 31B become lower than thethreshold value. For example, the switching unit 33 stops the supply ofelectric power from the battery 32 to the position detection system 1when the electric power generated from the electric signal generationunits 31A and 31B becomes lower than the threshold value. For example,in a case where a pulsed electric signal is generated in the electricsignal generation units 31A and 31B, the switching unit 33 starts thesupply of electric power from the battery 32 to the position detectionsystem 1 at the time when a level (electric power) of the electricsignal rises from a low level to a high level, and stops the supply ofelectric power from the battery 32 to the position detection system 1after a predetermined time elapses since the level (electric power) ofthe electric signal changes to the low level. Also, the encoder deviceEC has a configuration of using the electric signals (pulse signals)generated from the electric signal generation units 31A and 31B, as aswitching signal (trigger signal) for the supply of electric power fromthe battery 32 to the position detection system 1.

FIG. 2A is a perspective view showing the magnet 11, the electric signalgeneration units 31A and 31B, and two magnetic sensors 51 and 52 thatare the magnetism detection units 12 in FIG. 1 , FIG. 2B is a plan viewof the magnet 11 and the like in FIG. 2A, as seen from a directionparallel to the rotary shaft SF, and FIG. 2C is a circuit diagram of themagnetic sensor 51. Note that in FIG. 2A and the like, the rotary shaftSF of FIG. 1 is shown with a straight line. In FIGS. 2A and 2B, themagnet 11 is configured so that rotation changes the direction andstrength of the magnetic field in an axial direction that is a directionparallel to a straight line (symmetrical axis) passing through a centerof the rotary shaft SF. The magnet 11 is an annular member that iscoaxial with the rotary shaft SF, for example. As an example, the magnet11 is configured by a first annular magnet consisting of an N pole 16A,an S pole 16B, an N pole 16C, and an S pole 16D, which are sequentiallydisposed so as to surround the rotary shaft SF and each have an openingangle of 90° and a fan shape, and a second annular magnet consisting ofan S pole 17A, an N pole 17B, an S pole 17C, and an N pole 17D, whichhave the same shapes as the N pole 16A to the S pole 16D and are eachattached and disposed to one surface of the N pole 16A to the S pole16D. The magnet 11 is a permanent magnet that is magnetized to have fourpairs of polarities along a circumferential direction (or also referredto as a rotating direction) around the rotary shaft SF and generates amagnetic force. A front surface (a surface opposite to the motor M inFIG. 1 ) and a back surface (a surface on the same side as the motor M),which are main surfaces of the magnet 11, are each substantiallyperpendicular to the rotary shaft SF. In other words, in the magnet 11,the N pole 16A to the S pole 16D on the front surface-side and the Spole 17A to the N pole 17D on the back surface-side are offset by 90° inangle (for example, in positions of the respective N poles and the Spoles) (180° in phase), and boundaries between the N poles and the Spoles of the N pole 16A to the S pole 16D and boundaries between the Spoles and the N poles of the S pole 17A to the N pole 17D substantiallycoincide with each other with respect to positions in thecircumferential direction (angular positions). Note that the firstannular magnet and the second annular magnet may be one magnetintegrated continuously in the moving direction (for example, thecircumferential direction, the rotating direction) or the axialdirection and having a plurality of polarities or may be a hollow magnethaving a space at the inside of these magnets.

Herein, for convenience of descriptions, rotation in a counterclockwisedirection is referred to as forward rotation, and rotation in aclockwise direction is referred to as reverse rotation, as seen from atip end side of the rotary shaft SF (an opposite side to the motor M inFIG. 1 ). Also, an angle of the forward rotation is indicated by apositive value, and an angle of the reverse rotation is indicated by anegative value. Note that rotation in a counterclockwise direction maybe referred to as forward rotation, and rotation in a clockwisedirection may be referred to as reverse rotation, as seen from a rearend side of the rotary shaft SF (the motor M-side in FIG. 1 ).

Herein, in a coordinate system fixed to the magnet 11, an angularposition of a boundary between the S pole 16D and the N pole 16A in thecircumferential direction is denoted as a position 11 a, and angularpositions (boundaries between the N pole and the S pole) sequentiallyrotated by 90° from the position 11 a are each denoted as positions 11b, 11 c and 11 d. In a first section from the position 11 a to theposition 90° counterclockwise, the N pole is disposed on the frontsurface-side of the magnet 11, and the S pole is disposed on the backsurface-side of the magnet 11. In the first section, a direction of themagnetic field of the magnet 11 in the axial direction is substantiallyparallel to an axial direction AD1 (see FIG. 3C) from the frontsurface-side toward the back surface-side of the magnet 11. In the firstsection, the strength of the magnetic field is maximized in the middleof the position 11 a and the position 11 b, and is minimized near thepositions 11 a and 11 b.

In a second section of 90° in the counterclockwise direction from theposition 11 b (a section in which the S pole is disposed on the frontsurface-side of the magnet 11, and the N pole is disposed on the backsurface-side of the magnet 11), a direction of the magnetic field of themagnet 11 in the axial direction is substantially a direction from theback surface-side toward the front surface-side of the magnet 11 (forexample, an opposite direction to the axial direction AD1 (FIG. 3C)). Inthe second section, the strength of the magnetic field is maximized inthe middle of the position 11 b and the position 11 c, and is minimizednear the positions 11 b and 11 c. Similarly, in a third section from theposition 11 c to the position 90° counterclockwise and in a fourthsection from the position 11 d to the position 90° counterclockwise,directions of the magnetic fields of the magnet 11 in the axialdirection are substantially a direction from the front surface-sidetoward the back surface-side of the magnet 11 and a direction from theback surface-side toward the front surface-side of the magnet 11,respectively.

As such, the directions of the magnetic field formed by the magnet 11 inthe axial direction are sequentially reversed at the positions 11 a to11 d. The magnet 11 forms an AC magnetic field in which the direction ofthe magnetic field in the axial direction is reversed with the rotationof the magnet 11, with respect to the coordinate system fixed to theoutside of the magnet 11. The electric signal generation units 31A and31B are disposed on the outer surface of the magnet 11 in a directionintersecting with a normal direction of the main surfaces of the magnet11. In the present embodiment, the electric signal generation units 31Aand 31B are provided without contacting the magnet 11 with each goingaway in a diametrical direction (for example, a radial direction) of themagnet 11 orthogonal to the rotary shaft SF or in a direction parallelto the diametrical direction. The first electric signal generation unit31A includes a first magnetosensitive part 41A, a first electric powergeneration part 42A, and a first set of first magnetic body 45A and afirst set of second magnetic body 46A. Note that one of the firstmagnetic body 45A and the second magnetic body 46A may be omitted. Thefirst magnetosensitive part 41A, the first electric power generationpart 42A, the first magnetic body 45A, and the second magnetic body 46Aare fixed to the outside of the magnet 11, and relative positionsthereof to each position on the magnet 11 are changed with the rotationof the magnet 11. For example, in FIG. 2B, the position 11 b of themagnet 11 is disposed at a position 45° in the counterclockwise from thefirst electric signal generation unit 31A. When the magnet 11 rotatesone-turn in the forward direction (counterclockwise) from this state,the positions 11 a, 11 d, 11 c and 11 b sequentially pass near theelectric signal generation unit 31A.

The first magnetosensitive part 41A is a magnetosensitive wire such as aWiegand wire. In the first magnetosensitive part 41A, large Barkhausenjump (Wiegand effect) is generated by the change in magnetic fieldassociated with the rotation of the magnet 11. The firstmagnetosensitive part 41A is a cylindrical member whose projection imageis rectangular, and an axial direction thereof is set in thecircumferential direction of the magnet 11. Hereinafter, the axialdirection of the first magnetosensitive part 41A, i.e., a directionperpendicular to a circular (or which may be polygonal or the like)cross-section of the first magnetosensitive part 41A is referred to asthe length direction of the first magnetosensitive part 41A. Also, forexample, a length of the magnetosensitive part in the direction (theaxial direction, the length direction, the longitudinal direction)perpendicular to the cross-section of the magnetosensitive part (forexample, the first magnetosensitive part 41A) is set to be longer than alength of the magnetosensitive part in a direction (width direction)parallel to the cross-section of the magnetosensitive part. When the ACmagnetic field is applied in the axial direction (length direction) ofthe first magnetosensitive part 41A and the AC magnetic field isreversed, the first magnetosensitive part 41A generates a magneticdomain wall from one end toward the other end in the axial direction. Assuch, the length direction (axial direction) of the magnetosensitivepart (for example, the first magnetosensitive part 41A and the like) ofthe present embodiment is also referred to as an easy magnetizationdirection that is a direction in which magnetization is easily oriented.

The first and second magnetic bodies 45A and 46A are formed of aferromagnetic material such as iron, cobalt, nickel, for example. Thefirst and second magnetic bodies 45A and 46A can also be referred to asyokes. The first magnetic body 45A is provided between the front surfaceof the magnet 11 and one end of the first magnetosensitive part 41A, andthe second magnetic body 46A is provided between the back surface of themagnet 11 and the other end of the first magnetosensitive part 41A. Tipend portions of the first and second magnetic bodies 45A and 46A aredisposed at the same angular position in the circumferential directionon the front surface and back surface of the magnet 11. The polaritiesof the magnet 11 are always opposite to each other at the tip endportions of the first and second magnetic bodies 45A and 46A, and whenthe tip end portion of the first magnetic body 45A is positioned nearthe N pole 16A (or the S pole 16B), the tip end portion of the secondmagnetic body 46A is located near the S pole 17A (or the N pole 17B).For this reason, the first and second magnetic bodies 45A and 46A guidemagnetic field lines from the two parts of the magnet 11 (for example,the N pole 16A and the S pole 17A), which are located at the sameposition in the circumferential direction of the magnet 11 and havepolarities different from each other, to the length direction of thefirst magnetosensitive part 41A. By the magnet 11, the first magneticbody 45A, the first magnetosensitive part 41A, and the second magneticbody 46A, a magnetic circuit MC1 (see FIG. 3A) including the magneticfield lines toward the length direction of the first magnetosensitivepart 41A is formed. Note that a peripheral edge portion of the disc 15of FIG. 1 is provided with a step (not shown), so that a space intowhich the second magnetic body 46A can be inserted is secured betweenthe peripheral edge portion of the disc 15 and the back surface themagnet 11.

The first electric power generation part 42A is, for example, ahigh-density coil wound and disposed on the first magnetosensitive part41A. In the first electric power generation part 42A, electromagneticinduction is generated due to the generation of the magnetic domain wallin the first magnetosensitive part 41A, so that an induction currentflows. When the positions 11 a to 11 d of the magnet 11 shown in FIG. 2Bpass near the electric signal generation unit 31A (the tip end portionsof the magnetic bodies 45A and 46A), a pulsed current (electric signal,electric power) is generated in the first electric power generation part42A.

A direction of the current generated in the first electric powergeneration part 42A is changed in accordance with the direction of themagnetic field before and after the reversal. For example, a directionof the current that is generated upon the reversal from the magneticfield toward the front surface-side to the magnetic field toward theback surface-side of the magnet 11 is opposite to a direction of thecurrent that is generated upon the reversal from the magnetic fieldtoward the back surface-side to the magnetic field toward the frontsurface-side of the magnet 11. The electric power (induction current)that is generated in the first electric power generation part 42A can beset by the number of turns in the high-density coil, for example.

As shown in FIG. 2A, the first magnetosensitive part 41A, the firstelectric power generation part 42A, and the parts of the first andsecond magnetic bodies 45A and 46A on the first magnetosensitive part41A-side are accommodated in a case 43A. The case 43A is provided withterminals 42Aa and 42Ab. The high-density coil of the first electricpower generation part 42A has one end and the other end thereof that areelectrically connected to the terminals 42Aa and 42Ab, respectively. Theelectric power generated in the first electric power generation part 42Acan be extracted outside of the first electric signal generation unit31A via the terminals 42Aa and 42Ab.

The second electric signal generation unit 31B is disposed in an angularposition forming an angle larger than 0° and smaller than 180° from theangular position in which the first electric signal generation unit 31Ais disposed. An angle between the electric signal generation units 31Aand 31B is selected within a range from 22.5° to 67.5°, for example, andis about 45° in FIG. 2B. The second electric signal generation unit 31Bhas a similar configuration to the first electric signal generation unit31A. The second electric signal generation unit 31B includes a secondmagnetosensitive part 41B, a second electric power generation part 42B,and a second set of first magnetic body 45B and a second set of secondmagnetic body 46B. The second magnetosensitive part 41B, the secondelectric power generation part 42B, and the second set of first andsecond magnetic bodies 45B and 46B are similar to the firstmagnetosensitive part 41A, the first electric power generation part 42A,and the first set of first and second magnetic bodies 45A and 46A,respectively, and the descriptions thereof are thus omitted. The secondmagnetosensitive part 41B, the second electric power generation part42B, and the parts of the first and second magnetic bodies 45B and 46Bon the second magnetosensitive part 41B-side are accommodated in a case43B. The case 43B is provided with terminals 42Ba and 42Bb. The electricpower generated in the second electric power generation part 42B can beextracted outside of the second electric signal generation unit 31B viathe terminals 42Ba and 42Bb. Note that at least a part of themagnetosensitive part (for example, the first magnetosensitive part 41Aand the second magnetosensitive part 41B) is disposed spaced apartoutside of the magnet 11 in the diametrical direction of the magnet 11or in the parallel direction thereof. For example, when the surfaces(i.e., the surfaces on which the plurality of polarities of the magnetis aligned) of the magnet 11 orthogonal to the rotary shaft SF are eachreferred to as one surface and the other surface, the magnetosensitivepart is disposed spaced apart outside with respect to a side surface (ora side surface parallel to the axial direction of the rotary shaft SF)of the magnet 11 orthogonal to one surface or the other surface of themagnet 11 and along the moving direction of the magnet.

The magnetism detection unit 12 includes magnetic sensors 51 and 52. Themagnetic sensor 51 is disposed in an angular position greater than 0°and smaller than 180° with respect to the second magnetosensitive part41B (second electric signal generation unit 31B) in the rotatingdirection of the rotary shaft SF. The magnetic sensor 52 is disposed inan angular position (about 45°, in FIG. 2B) greater than 22.5° andsmaller than 67.5° with respect to the magnetic sensor 51 in therotating direction of the rotary shaft SF.

As shown in FIG. 2C, the magnetic sensor 51 includes a magnetoresistiveelement 56, a bias magnet (not shown) for applying a magnetic fieldhaving predetermined strength to the magnetoresistive element 56, and awaveform shaping circuit (not shown) for shaping a waveform from themagnetoresistive element 56. The magnetoresistive element 56 has a fullbridge shape where elements 56 a, 56 b, 56 c and 56 d are connected inseries. A signal line between the elements 56 a and 56 c is connected toa power supply terminal 51 p, and a signal line between the elements 56b and 56 d is connected to a ground terminal 51 g. A signal line betweenthe elements 56 a and 56 b is connected to a first output terminal 51 a,and a signal line between the elements 56 c and 56 d is connected to asecond output terminal 51 b. The magnetic sensor 52 has a similarconfiguration to the magnetic sensor 51, and the descriptions thereofare thus omitted.

Subsequently, operations of the first electric signal generation unit31A of the present embodiment are described. Hereinafter, the firstmagnetosensitive part 41A and the first electric power generation part42A of the first electric signal generation unit 31A shown in FIG. 2Bare collectively described as a magnetosensitive member 47. A lengthdirection of the magnetosensitive member 47 is the same as the lengthdirection of the first magnetosensitive part 41A, and the center in thelength direction of the magnetosensitive member 47 is the same as thecenter in the length direction of the first magnetosensitive part 41A.Note that since operations of the second electric signal generation unit31B are similar to those of the first electric signal generation unit31A, the descriptions thereof are omitted.

FIG. 3A is a plan view depicting the magnet 11 and the electric signalgeneration unit 31A shown in FIG. 2A, and FIGS. 3B and 3C are sectionalviews of the magnet 11 shown in FIG. 3A. In FIGS. 3A and 3B, the magnet11 has a flat plate shape along a rotating direction (hereinafter, alsoreferred to as the θ direction) around the rotary shaft SF, has aplurality of polarities (the N pole 16A to the S pole 16D) differentfrom each other in the θ direction, and has two polarities (the N pole16A and the S pole 17A, and the like) different from each other in athickness direction (in the present embodiment, the axial direction AD1of the rotary shaft SF) orthogonal to the 0 direction. For this reason,the axial direction AD1 can also be referred to as an orientationdirection (magnetization direction) of parts of the magnet 11 havingpolarities different from each other (the N pole 16A, the S pole 17A,and the like). As the magnet 11 rotates in the θ direction, thedirection and strength of the magnetic field in the axial direction orthe orientation direction AD1 are changed.

Also, the magnetosensitive member 47 (or the magnetosensitive part) isdisposed near the outer surface of the magnet 11 so that the lengthdirection thereof is parallel to the front surface (one surface or backsurface) of the magnet 11 having a flat plate shape. In FIG. 3A, whenthe length direction of the magnetosensitive member 47 is referred to asa direction LD1, the length direction LD1 is parallel to the frontsurface of the magnet 11. In the present embodiment, the lengthdirection LD1 of the magnetosensitive member 47 is substantiallyparallel to the θ direction (circumferential direction), and is alsosubstantially orthogonal to the axial direction AD1 that is themagnetization direction of the magnet 11 (for example, a specificdirection in which a direction of a magnetic pole is fixed). Also, asshown in FIG. 3C, the length direction of the magnetosensitive member 47is disposed so as to be substantially orthogonal to a tangentialdirection (herein, a direction parallel to the axial direction AD1) of amagnetic field line MF1, which passes through a substantial center (forexample, a position of a half of a length in the length direction of themagnetosensitive member 47 or the magnetosensitive part (41A, 41B)) inthe length direction of the magnetosensitive member 47, of the magneticfield lines of the magnet 11. Note that the length direction LD1 of themagnetosensitive member 47 is disposed so as to be substantiallyorthogonal to the thickness direction orthogonal to the θ direction.Also, the first and second magnetic bodies 45A and 46A guide magneticfield lines from the two parts of the magnet 11 (for example, the N pole16A and the S pole 17A), which are located at the same angular positionin the θ direction and have polarities different from each other, to thelength direction LD1 of the magnetosensitive member 47 via one end 47 aand the other end 47 b of the magnetosensitive member 47.

A magnetic field component unnecessary for pulse generation in theelectric signal generation unit 31A including magnetic field linesgenerated on a side surface of the magnet 11 is orthogonal to the lengthdirection of the magnetosensitive member 47, and the unnecessarymagnetic field component does not adversely affect the generation of themagnetic domain wall from one end toward the other end of themagnetosensitive member 47 due to large Barkhausen jump (Wiegand effect)in the length direction of the magnetosensitive member 47 caused by thereversal of the AC magnetic field due to the rotation of the magnet 11.For this reason, even when the magnetosensitive member 47 is disposednear the magnet 11 and the electric signal generation unit 31A is thusdownsized, it is possible to effectively generate the stable high-outputpulse by using the electric signal generation unit 31A through thereversal of the AC magnetic field in the axial direction due to therotation of the magnet 11, without being affected by the unnecessarymagnetic field component.

FIG. 4 shows a circuit configuration of the electric power supplyingsystem 2 and the multi-turn information detection unit 3 in accordancewith the present embodiment. In FIG. 4 , the electric power supplyingsystem 2 includes the first electric signal generation unit 31A, arectifier stack 61, the second electric signal generation unit 31B, arectifier stack 62, and the battery 32. Also, the electric powersupplying system 2 includes a regulator 63, as the switching unit 33shown in FIG. 1 . The rectifier stack 61 is a rectifier that rectifies acurrent flowing from the first electric signal generation unit 31A. Afirst input terminal 61 a of the rectifier stack 61 is connected to theterminal 42Aa of the first electric signal generation unit 31A. A secondinput terminal 61 b of the rectifier stack 61 is connected to theterminal 42Ab of the first electric signal generation unit 31A. A groundterminal 61 g of the rectifier stack 61 is connected to a ground line GLto which the same potential as a signal ground SG is supplied. Duringthe operation of the multi-turn information detection unit 3, thepotential of the ground line GL becomes a reference potential of thecircuit. An output terminal 61 c of the rectifier stack 61 is connectedto a control terminal 63 a of the regulator 63.

The rectifier stack 62 is a rectifier that rectifies a current flowingfrom the second electric signal generation unit 31B. A first inputterminal 62 a of the rectifier stack 62 is connected to the terminal42Ba of the second electric signal generation unit 31B. A second inputterminal 62 b of the rectifier stack 62 is connected to the terminal42Bb of the second electric signal generation unit 31B. A groundterminal 62 g of the rectifier stack 62 is connected to the ground lineGL. An output terminal 62 c of the rectifier stack 62 is connected tothe control terminal 63 a of the regulator 63.

The regulator 63 regulates electric power that is supplied from thebattery 32 to the position detection system 1. The regulator 63 mayinclude a switch 64 provided on an electric power supply path betweenthe battery 32 and the position detection system 1. The regulator 63controls an operation of the switch 64, based on the electric signalsgenerated from the electric signal generation units 31A and 31B. Aninput terminal 63 b of the regulator 63 is connected to the battery 32.An output terminal 63 c of the regulator 63 is connected a power supplyline PL. A ground terminal 63 g of the regulator 63 is connected to theground line GL. The control terminal 63 a of the regulator 63 is anenable terminal, and the regulator 63 keeps a potential of the outputterminal 63 c to a predetermined voltage in a state where a voltageequal to or higher than a threshold value is applied to the controlterminal 63 a. An output voltage (predetermined voltage) of theregulator 63 is, for example, 3V when a counter 67 is configured by aCMOS and the like. An operating voltage of a non-volatile memory 68 ofthe storage unit 14 is set to the same voltage as the predeterminedvoltage, for example. Note that the predetermined voltage is a voltagenecessary for electric power supply, and may be not only a constantvoltage value, but also a voltage changing in a stepwise manner.

A first terminal 64 a of the switch 64 is connected to the inputterminal 63 b, and a second terminal 64 b is connected to the outputterminal 63 c. The regulator 63 switches conduction and insulationstates between the first terminal 64 a and the second terminal 64 b ofthe switch 64 by using the electric signals supplied from the electricsignal generation units 31A and 31B to the control terminal 63 a, as acontrol signal (enable signal). For example, the switch 64 includes aswitching device such as a MOS, a TFT and the like, the first terminal64 a and the second terminal 64 b are a source electrode and a drainelectrode, and a gate electrode is connected to the control terminal 63a. The switch 64 is in a state (on state) where the source electrode andthe drain electrode can be conductive therebetween, when the gateelectrode is charged by the electric signals (electric power) generatedfrom the electric signal generation units 31A and 31B and a potential ofthe gate electrode becomes equal to or higher than a threshold value.Note that the switch 64 may also be provided outside the regulator 63,and may be externally attached such as a relay, for example.

The multi-turn information detection unit 3 includes, as the magnetismdetection unit 12, the magnetic sensors 51 and 52, and analogcomparators 65 and 66. The magnetism detection unit 12 detects themagnetic field formed by the magnet 11 by using the electric powersupplied from the battery 32. Also, the multi-turn information detectionunit 3 includes a counter 67, as the detection unit 13 shown in FIG. 1 ,and includes a non-volatile memory 68, as the storage unit 14. Theelectric power supply terminal 51 p of the magnetic sensor 51 isconnected to the power supply line PL. The ground terminal 51 g of themagnetic sensor 51 is connected to the ground line GL. An outputterminal 51 c of the magnetic sensor 51 is connected to an inputterminal 65 a of the analog comparator 65. In the present embodiment,the output terminal 51 c of the magnetic sensor 51 outputs a voltagecorresponding to a difference between a potential of the second outputterminal 51 b shown in FIG. 2C and the reference potential. The analogcomparator 65 is a comparator that compares a voltage output from themagnetic sensor 51 with a predetermined voltage. A power supply terminal65 p of the analog comparator 65 is connected to the power supply linePL. A ground terminal 65 g of the analog comparator 65 is connected tothe ground line GL. An output terminal 65 b of the analog comparator 65is connected to a first input terminal 67 a of the counter 67. Theanalog comparator 65 outputs an H-level signal from the output terminalwhen an output voltage of the magnetic sensor 51 is equal to or higherthan a threshold value, and outputs an L-level signal from the outputterminal when the output voltage of the magnetic sensor 51 is lower thanthe threshold value.

The magnetic sensor 52 and the analog comparator 66 have similarconfigurations to the magnetic sensor 51 and the analog comparator 65. Apower supply terminal 52 p of the magnetic sensor 52 is connected to thepower supply line PL. A ground terminal 52 g of the magnetic sensor 52is connected to the ground line GL. An output terminal 52 c of themagnetic sensor 52 is connected to an input terminal 66 a of the analogcomparator 66. A power supply terminal 66 p of the analog comparator 66is connected to the power supply line PL. A ground terminal 66 g of theanalog comparator 66 is connected to the ground line GL. An outputterminal 58 b of the analog comparator 66 is connected to a second inputterminal 67 b of the counter 67. The analog comparator 66 outputs anH-level signal from the output terminal when an output voltage of themagnetic sensor 52 is equal to or higher than a threshold value, andoutputs an L-level signal from the output terminal 66 b when the outputvoltage of the magnetic sensor 52 is lower than the threshold value.

The counter 67 counts the multi-turn information of the rotary shaft SFby using the electric power supplied from the battery 32. The counter 67includes, for example, a CMOS logical circuit and the like. The counter67 operates using the electric power that is supplied via a power supplyterminal 6′7 p and a ground terminal 67 g. The power supply terminal 6′7p of the counter 67 is connected to the power supply line PL. The groundterminal 67 g of the counter 67 is connected to the ground line GL. Thecounter 67 performs counting processing by using a voltage that issupplied via the first input terminal 67 a, and a voltage that issupplied via the second input terminal 67 b, as a control signal.

The non-volatile memory 68 stores at least a part (for example, themulti-turn information) of the rotational position information detectedby the detection unit 13 by using the electric power supplied from thebattery 32 (performs a writing operation). The non-volatile memory 68stores a result (multi-turn information) of the counting by the counter67, as the rotational position information detected by the detectionunit 13. A power supply terminal 68 p of the non-volatile memory 68 isconnected to the power supply line PL. A ground terminal 68 g of thestorage unit 14 is connected to the ground line GL. The storage unit 14shown in FIG. 1 includes the non-volatile memory 68, and can keep theinformation written while the electric power is supplied, even in astate where the electric power is not supplied.

In the present embodiment, a capacitor 69 is provided between therectifier stacks 61 and 62 and the regulator 63. A first electrode 69 aof the capacitor 69 is connected to a signal line for connecting therectifier stacks 61 and 62 and the control terminal 63 a of theregulator 63. A second electrode 69 b of the capacitor 69 is connectedto the ground line GL. The capacitor 69 is a so-called smoothingcapacitor, and reduces pulsation to reduce a load of the regulator. Aconstant of the capacitor 69 is set so that the electric power supplyfrom the battery 32 to the detection unit 13 and the storage unit 14 iskept for a time period in which the rotational position information isdetected by the detection unit 13 and the rotational positioninformation is written into the storage unit 14, for example.

Also, the battery 32 includes, for example, a primary battery 36 such asa button-shaped battery and a rechargeable secondary battery 37. Thesecondary battery 37 is electrically connected to a power supply unitMCE of the motor control unit MC. During at least a part of a timeperiod (for example, a time period in which a main power supply is in anon state) in which the power supply unit MCE of the motor control unitMC can supply the electric power, the electric power is supplied fromthe power supply unit MCE to the secondary battery 37, and the secondarybattery 37 is recharged by the electric power. During a time period (forexample, a time period in which a main power supply is in an off state)in which the power supply unit MCE of the motor control unit MC cannotsupply the electric power, the supply of the electric power from thepower supply unit MCE to the secondary battery 37 is cut off.

Also, the secondary battery 37 may be electrically connected to atransmission path of the electric signals from the electric signalgeneration units 31A and 31B. In this case, the secondary battery 37 canbe recharged by the electric power of the electric signals from theelectric signal generation units 31A and 31B. For example, the secondarybattery 37 is electrically connected to a circuit between the rectifierstack 61 and the regulator 63. The secondary battery 37 can be rechargedby the electric power of the electric signals that are generated fromthe electric signal generation units 31A and 31B by the rotation of therotary shaft SF, in a state where the supply of the electric power fromthe power supply unit MCE is cut off. Note that the secondary battery 37may also be recharged by the electric power of the electric signals thatare generated from the electric signal generation units 31A and 31B asthe motor M is driven to rotate the rotary shaft SF.

The encoder device EC in accordance with the present embodiment selectsto supply the electric power from which of the primary battery 36 andthe secondary battery 37 to the position detection system 1, in a statewhere the supply of the electric power from an outside is cut off. Theelectric power supplying system 2 includes a power supply switcher (apower supply selection unit, a selection unit) 38, and the power supplyswitcher 38 switches (selects) to supply the electric power from whichof the primary battery 36 and the secondary battery 37 to the positiondetection system 1. A first input terminal of the power supply switcher38 is electrically connected to a positive electrode of the primarybattery 36, and a second input terminal of the power supply switcher 38is electrically connected to the secondary battery 37. An outputterminal of the power supply switcher 38 is electrically connected tothe input terminal 63 b of the regulator 63.

The power supply switcher 38 selects the primary battery 36 or thesecondary battery 37, as the battery for supplying the electric power tothe position detection system 1, based on a remaining amount of thesecondary battery 37, for example. For example, when a remaining amountof the secondary battery 37 is equal to or greater than a thresholdvalue, the power supply switcher 38 supplies the electric power from thesecondary battery 37, and does not supply the electric power from theprimary battery 36. The threshold value is set, based on electric powerthat is consumed in the position detection system 1, and is set equal toor higher than the electric power that is to be supplied to the positiondetection system 1, for example. For example, when the electric powerthat is consumed in the position detection system 1 can be covered bythe electric power that from the secondary battery 37, the power supplyswitcher 38 supplies the electric power from the secondary battery 37,and does not supply the electric power from the primary battery 36.Also, when the remaining amount of the secondary battery 37 is less thanthe threshold value, the power supply switcher 38 supplies the electricpower from the primary battery 36, and does not supply the electricpower from the secondary battery 37. The power supply switcher 38 mayalso serve as a charger for controlling the recharging of the secondarybattery 37, for example, and may determine whether the remaining amountof the secondary battery 37 is equal to or greater than the thresholdvalue by using remaining amount information of the secondary battery 37that is used for control of the recharging.

The secondary battery 37 is used in a combined manner in this way, sothat it is possible to delay the consumption of the primary battery 36.Therefore, the encoder device EC has no maintenance (for example,replacement) of the battery 32 or the maintenance frequency is low. Notethat the battery 32 may include at least one of the primary battery 36and the secondary battery 37. Also, in the above embodiment, theelectric power is alternatively supplied from the primary battery 36 orthe secondary battery 37. However, the electric power may be suppliedfrom both the primary battery 36 and the secondary battery 37. Forexample, a processing unit to which the primary battery 36 supplies theelectric power and a processing unit to which the secondary battery 37supplies the electric power may be determined, in accordance with powerconsumption of each processing unit (for example, the magnetic sensor51, the counter 67 and the non-volatile memory 68) of the positiondetection system 1. Note that the secondary battery 37 may be rechargedusing at least one of the electric power that is supplied from a powersupply unit EC2 and the electric power of the electric signals that aregenerated from the electric signal generation units 31A and 31B.

Subsequently, operations of the electric power supplying system 2 andthe multi-turn information detection unit 3 are described. FIG. 5 is atiming chart showing operations of the multi-turn information detectionunit 3 when the rotary shaft SF rotates in the counterclockwisedirection (forward rotation). Since a timing chart showing operations ofthe multi-turn information detection unit 3 when the rotary shaft SFrotates in the counterclockwise direction (reverse rotation) is invertedto the chart of FIG. 4 over time, the descriptions thereof are omitted.

In “Magnetic field” of FIG. 5 , a solid line indicates a magnetic fieldat the position of the first electric signal generation unit 31A, and abroken line indicates a magnetic field at the position of the secondelectric signal generation unit 31B. “First electric signal generationunit”, and “Second electric signal generation unit” indicate an outputof the first electric signal generation unit 31A and an output of thesecond electric signal generation unit 31B, respectively, and an outputof current flowing in one direction is denoted as positive (+), and anoutput of current flowing in an opposite direction thereof is denoted asnegative (−). “Enable signal” indicates a potential that is applied tothe control terminal 63 a of the regulator 63 by the electric signalsgenerated from the electric signal generation units 31A and 31B, and ahigh level is denoted as “H” and a low level is denoted as “L”.“Regulator” indicates an output of the regulator 63, and a high level isdenoted as “H” and a low level is denoted as “L”.

In FIG. 5 , “Magnetic field on first magnetic sensor” and “Magneticfield on second magnetic sensor” are magnetic fields formed on themagnetic sensors 51 and 52. The magnetic field formed by the magnet 11is shown with a long broken line, the magnetic field formed by a biasmagnet is shown with a short broken line, and a synthetic magnetic fieldthereof is shown with a solid line. “First magnetic sensor” and “Secondmagnetic sensor” each indicate outputs when the magnetic sensors 51 and52 are constantly driven, an output from the first output terminal isshown with a broken line, and an output from the second output terminalis shown with a solid line. “First analog comparator” and “Second analogcomparator” indicate outputs from the analog comparators 65 and 66,respectively. An output when the magnetic sensor and the analogcomparator are constantly driven is denoted as “constant drive”, and anoutput when the magnetic sensor and the analog comparator areintermittently driven is denoted as “intermittent drive”.

When the rotary shaft SF rotates in the counterclockwise direction, thefirst electric signal generation unit 31A outputs the current pulseflowing in the forward direction (“+” of “first electric signalgeneration unit”), at the angular positions of 45° and 225°. Also, thefirst electric signal generation unit 31A outputs the current pulseflowing in the reverse direction (“−” of “first electric signalgeneration unit”), at the angular positions of 135° and 315°. The secondelectric signal generation unit 31B outputs the current pulse flowing inthe reverse direction (“−” of “second electric signal generation unit”),at the angular positions of 90° and 270°. Also, the second electricsignal generation unit 31B outputs the current pulse flowing in theforward direction (“−” of “second electric signal generation unit”), atthe angular positions of 180° and 0° (360°). For this reason, the enablesignal is switched to a high level at each of the angular positions of45°, 90°, 135°, 180°, 225°, 270°, 315°, and 0°. Also, the regulator 63supplies a predetermined voltage to the power supply line PL at each ofthe angular positions of 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 0°,in a state where the enable signal is held at the high level.

In the present embodiment, the output of the magnetic sensor 51 and theoutput of the magnetic sensor 52 have a phase difference of 90°, and thedetection unit 13 detects the rotational position information by usingthe phase difference. The output of the magnetic sensor 51 is a positivesine wave in a range from the angular position 22.5° to the angularposition 112.5°. In the angle range, the regulator 63 outputs theelectric power at the angular positions of 45° and 90°. The magneticsensor 51 and the analog comparator 65 are driven by the electric powersupplied at each of the angular positions of 45° and 90°. A signal(hereinafter, referred to as “A-phase signal”) that is output from theanalog comparator 65 is kept at an L-level in a state where the electricpower is not supplied, and is an H-level at each of the angularpositions of 45° and 90°.

Also, the output of the magnetic sensor 52 is a positive sine wave in arange from the angular position of 157.5° to the angular position of247.5°. In the angle range, the regulator 63 outputs the electric powerat the angular positions of 180° and 225°. The magnetic sensor 52 andthe analog comparator 66 are driven by the electric power supplied ateach of the angular positions of 180° and 225°. A signal (hereinafter,referred to as “B-phase signal”) that is output from the analogcomparator 66 is kept at an L-level in a state where the electric poweris not supplied, and is an H-level at each of the angular positions of180° and 225°.

Herein, when the A-phase signal supplied to the counter 67 is an H-level(H) and the B-phase signal supplied to the counter 67 is an L-level, aset of the signal levels is denoted as (H, L). In FIG. 5 , a set of thesignal levels at the angular position of 180° is (L, H), a set of thesignal levels at the angular position of 225° is (H, H), and a set ofthe signal levels at the angular position of 270° is (H, L).

When one or both of the detected A-phase signal and B-phase signal is anH-level, the counter 67 stores the set of the signal levels in thestorage unit 14. When one or both of the A-phase signal and B-phasesignal detected next time is an H-level, the counter 67 reads out theset of the previous signal levels from the storage unit 14 and comparesthe set of the previous signal levels and a set of the current signallevels to determine the rotating direction of the rotary shaft SF. Forexample, when the set of the previous signal levels is (H, H) and theset of the current signal levels is (H, L), since the angular positionin the previous detection is 225° and the angular position in thecurrent detection is 270°, it can be seen that it is a counterclockwisedirection (forward rotation). When the set of the current signal levelsis (H, L) and the set of the previous signal levels is (H, H), thecounter 67 supplies an up signal, which indicates that the counter willbe counted up, to the storage unit 14. When the up signal from thecounter 67 is detected, the storage unit 14 updates the storedmulti-turn information to a value increased by 1. In this way, themulti-turn information detection unit 3 in accordance with the presentembodiment can detect the multi-turn information while determining therotating direction of the rotary shaft SF.

In this way, the encoder device EC in accordance with the presentembodiment comprises the position detection system 1 (position detectionunit) that detects the rotational position information of the rotaryshaft SF (moving part) of the motor M (power supplying unit); the magnet11 that rotates in conjunction with the rotary shaft SF and has aplurality of polarities along the rotating direction of the rotary shaftSF (the moving direction or the θ direction); and the electric signalgeneration unit 31A (electric signal generation unit) that has themagnetosensitive member 47 (magnetosensitive part 41A) whose magneticcharacteristic is changed by the change in magnetic field associatedwith relative movement to the magnet 11, and generates the electricsignal, based on the magnetic characteristic of the magnetosensitivemember 47, wherein the magnetosensitive member 47 is disposed so thatmagnetosensitive member 47 is spaced apart from a side surface of themagnet 11 in the direction orthogonal to the rotating direction and thelength direction of the magnetosensitive member 47 is orthogonal to thetangential directions of at least some of the magnetic field lines MF2of the magnet 11.

According to the present embodiment, a magnetic field componentunnecessary for pulse generation in the electric signal generation unit31A including magnetic field lines generated on the side surface of themagnet 11 is orthogonal to the length direction of the magnetosensitivemember 47, and the unnecessary magnetic field component does notadversely affect the generation of the magnetic domain wall from one endtoward the other end in the length direction of the magnetosensitivemember 47 caused by the reversal of the AC magnetic field due to therotation of the magnet 11. For this reason, even when themagnetosensitive member 47 is disposed near the magnet 11 and theelectric signal generation unit 31A is thus made small, it is possibleto effectively generate the high-output pulse (electric signal) withhigh reliability (stable output) by using the electric signal generationunit 31A through the reversal of the AC magnetic field in the axialdirection due to the rotation of the magnet 11, without being affectedby the unnecessary magnetic field component. Also, in a case where theencoder device EC comprises the battery 32, it is possible to omit themaintenance (for example, replacement) of the battery 32 or to reducethe maintenance frequency of the battery 32 by using the electric signaleffectively generated from the electric signal generation unit 31A.

Note that in order to suppress the effect of the magnetic fieldcomponent unnecessary for pulse generation in the electric signalgeneration unit 31A, it is also considered to cover the circumference ofthe magnetosensitive member 47 with a magnetic body. However, when thecircumference of the magnetosensitive member 47 is covered with themagnetic body, the electric signal generation unit becomes larger, whichincreases the cost and makes it difficult to incorporate the electricsignal generation unit into the drive device. Also, a resonance point ofthe electric signal generation unit 31A is lowered, so that it maybecome weak against vibration shock.

Also, in the encoder device EC, the electric power is supplied from thebattery 32 to the multi-turn information detection unit 3 in a shorttime after the electric signal is generated from the electric signalgeneration unit 31A, so that the multi-turn information detection unit 3is dynamically driven (intermittently driven). After the detection andwriting of the multi-turn information are over, the power delivery tothe multi-turn information detection unit 3 is cut off but the countedvalue is kept because it is stored in the storage unit 14. The sequenceis repeated each time the predetermined position on the magnet 11 passesnear the electric signal generation unit 31A, even in a state where thesupply of the electric power from the outside is cut off. Also, themulti-turn information stored in the storage unit 14 is read by themotor control unit MC and the like when the motor M starts next time,and is used to calculate an initial position of the rotary shaft SF, andthe like. In the encoder device EC, the battery 32 supplies at least apart of the electric power that is consumed in the position detectionsystem 1, in accordance with the electric signal generated from theelectric signal generation unit 31A. Therefore, it is possible toincrease the lifetime of the battery 32. For this reason, it is possibleto omit the maintenance (for example, replacement) of the battery 32 orto reduce the maintenance frequency of the battery 32. For example, whenthe lifetime of the battery 32 is longer than other parts of the encoderdevice EC, it may be unnecessary to replace the battery 32.

In the meantime, when a magnetosensitive wire such as a Wiegand wire isused, the pulse current (electric signal) is obtained from the electricsignal generation unit 31A even though the magnet 11 is rotated atextremely low speed. For this reason, for example, in the state wherethe electric power is not supplied to the motor M, even though therotary shaft SF (magnet 11) is rotated at extremely low speed, theoutput of the electric signal generation unit 31A can be used as theelectric signal. Note that as the magnetosensitive wire (firstmagnetosensitive part 41A), an amorphous magnetostrictive wire and thelike can also be used. In this case, for example, the encoder device ECmay perform full-wave rectification on the electric signal (current)generated from the electric signal generation unit (for example, 31A and31B) by using the rectifier stack (for example, a rectifier), and tosupply the rectified electric power to the multi-turn informationdetection unit 3 and the like.

Also, in the present embodiment, as shown in FIG. 3A, since the tip endportions of the first and second magnetic bodies 45A and 46A of theelectric signal generation unit 31A are disposed near the parts whosepolarities are different from each other at the same angular positionson the front surface (N pole 16A to the S pole 16D) and back surface (Spole 17A to the N pole 17D) of the magnet 11, the electric signalgeneration unit 31A can be made further smaller. Note that like anelectric signal generation unit 31C of a modified embodiment shown inFIGS. 3D and 3E, a tip end portion of a first magnetic body 45C on oneend-side of the magnetosensitive member 47 may be disposed near a part(for example, the N pole 16A, the S pole 16B or the like) having anypolarity on the front surface of the magnet 11, and a tip end portion ofa second magnetic body 46C on the other end-side of the magnetosensitivemember 47 may be disposed near a part (for example, the S pole 16D, theN pole 16A or the like) having different polarity on the front surfaceof the magnet 11. In this case, the first and second magnetic bodies 45Cand 46C guide the magnetic field lines from the two parts (for example,the N pole 16A and the S pole 16D) of the magnet 11, which are locatedat different positions in the rotating direction and have polaritiesdifferent from each other, to the length direction of themagnetosensitive member 47. Also in the electric signal generation unit31C, a magnetic circuit MC2 is formed from the magnet 11 so as to passthe first magnetic body 45C, the magnetosensitive member 47 and thesecond magnetic body 46C. Therefore, the magnetosensitive member 47 caneffectively output the stable pulse by the reversal of the AC magneticfield due to the rotation of the magnet 11, without being affected bythe unnecessary magnetic field on the side surface of the magnet 11.

In the above embodiment, the two electric signal generation units 31Aand 31B are provided. However, the encoder device EC may comprise onlyone electric signal generation unit 31A. Also, the encoder device EC maycomprise three or more electric signal generation units. Also, in otherembodiments and modified embodiments thereof to be described later, oneelectric signal generation unit will be described. However, a pluralityof electric signal generation units may be provided.

Second Embodiment

A second embodiment is described with reference to FIGS. 6A to 6E. Notethat in FIGS. 6A to 6D, the parts corresponding to FIGS. 3A to 3C aredenoted with the same reference signs, and the detailed descriptionsthereof are omitted. FIG. 6A is a plan view showing a magnet 11A and anelectric signal generation unit 31D of an encoder device in accordancewith the present embodiment, FIG. 6B is a side view of FIG. 6A, and FIG.6C is an enlarged view showing a part of FIG. 6A. In FIGS. 6A and 6B,the magnet 11A is configured so that the direction and strength of themagnetic field in a radial direction (or the diametrical direction, or aradiation direction) AD2 with respect to the rotary shaft SF are changedby rotation. The magnet 11A is, for example, an annular member that iscoaxial with the rotary shaft SF. The main surfaces (front surface andback surface) of the magnet 11A are substantially perpendicular to therotary shaft SF, respectively.

The magnet 11A includes an annular magnet on an outer periphery-sidewhere an N pole 16E and an S pole 16F are alternately disposed in therotating direction or the circumferential direction (θ direction) of therotary shaft SF and an annular magnet on an inner periphery-side wherean S pole 17E and an N pole 17F are alternately disposed in the θdirection. Phases of the annular magnet on the outer periphery-side andthe annular magnet on the inner periphery-side are offset by 180°. Inthe magnet 11A, a boundary between the S pole 17E and the N pole 17F onthe inner periphery-side substantially matches a boundary between the Npole 16E and the S pole 16F on the outer periphery-side, with respect tothe angular position in the θ direction. The magnet 11A has a flat plateshape along the θ direction, and a plurality of polarities (the N pole16E, the S pole 16F and the like) along the θ direction. Also, in themagnet 11A, a direction orthogonal to the rotating direction (movingdirection), i.e., in the present embodiment, the radial direction AD2with respect to the rotary shaft SF is regarded as a width direction ofthe magnet 11A. The magnet 11A has polarities (the N pole 16E, the Spole 17E and the like) different from each other in the width direction(radial direction AD2) orthogonal to the θ direction, on the frontsurface or back surface. The magnet 11A is a permanent magnet magnetizedto have a plurality of pairs of polarities (for example, 12 pairs) inthe θ direction. In the present embodiment, a magnetization direction(orientation direction) of the magnet 11A is the radial direction AD2.

In the present embodiment, the magnetosensitive member 47 of theelectric signal generation unit 31D is disposed so that the lengthdirection LD2 is orthogonal to the front surface of the magnet 11Ahaving a flat plate shape, in the vicinity of an outer surface of themagnet 11A. Also, the length direction LD2 of the magnetosensitivemember 47 in the electric signal generation unit 31D is disposed to beorthogonal to the radial direction AD2 with being spaced in thediametrical direction (for example, the radial direction) of the magnet11A orthogonal to the rotary shaft SF or in a direction parallel to thediametrical direction. In this case, the length direction LD2 isparallel to the axial direction of the rotary shaft SF. In other words,in the present embodiment, the length direction LD2 of themagnetosensitive member 47 is substantially orthogonal to the radialdirection AD2 that is the magnetization direction of the magnet 11A, andis also substantially orthogonal to the θ direction (circumferentialdirection). Also, a tip end portion of a first magnetic body 45D on oneend-side of the magnetosensitive member 47 is disposed near an outersurface of a part of one polarity (for example, the N pole 16E) on theouter periphery-side of the magnet 11A, and a tip end portion of asecond magnetic body 46D on the other end-side of the magnetosensitivemember 47 is disposed near an outer surface of a part (for example, theS pole 16F) of the other polarity (polarity different from the onepolarity) on the outer periphery-side of the magnet 11A. In other words,the first and second magnetic bodies 45D and 46D guide the magneticfield lines from the two parts (for example, the N pole 16E and the Spole 16F) of the magnet 11A, which are located at different positions inthe θ direction and have polarities different from each other, to thelength direction LD2 of the magnetosensitive member 47. The otherconfigurations are similar to the first embodiment.

Also in the present embodiment, a magnetic circuit MC3 is formed fromthe magnet 11A so as to pass the first magnetic body 45D, themagnetosensitive member 47, and the second magnetic body 46D. Also, asshown in FIG. 6C, the length direction of the magnetosensitive member 47is disposed so as to be substantially orthogonal to a tangentialdirection (herein, the θ direction) of the magnetic field line MF2,which passes through a substantial center in the length direction of themagnetosensitive member 47, of the magnetic field lines generated on theside surface of the magnet 11A.

A magnetic field component unnecessary for pulse generation in theelectric signal generation unit 31D including magnetic field linesgenerated on the side surface of the magnet 11A is orthogonal to thelength direction of the magnetosensitive member 47, and the unnecessarymagnetic field component does not adversely affect the generation of themagnetic domain wall from one end toward the other end of themagnetosensitive member 47 caused by the reversal of the AC magneticfield due to the rotation of the magnet 11A. For this reason, even whenthe magnetosensitive member 47 is disposed near the magnet 11A and theelectric signal generation unit 31D is thus made small, it is possibleto effectively generate the high-output pulse (electric signal) by usingthe electric signal generation unit 31D through the reversal of the ACmagnetic field in the radial direction AD2 due to the rotation of themagnet 11A, without being affected by the unnecessary magnetic fieldcomponent. Also, in a case where the encoder device comprises thebattery 32, it is possible to omit the maintenance (for example,replacement) of the battery 32 or to reduce the maintenance frequency ofthe battery 32 by using the electric signal effectively generated fromthe electric signal generation unit 31D.

Note that in the present embodiment, like an electric signal generationunit 31E of a modified embodiment shown in FIGS. 6D and 6E, a tip endportion of a first magnetic body 45E on one end-side of themagnetosensitive member 47 may be disposed near a part (for example, theN pole 16E, the S pole 16F or the like) of one polarity on the outerperiphery-side of the magnet 11A, and a tip end portion of a secondmagnetic body 46E on the other end-side of the magnetosensitive member47 may be disposed near a part (for example, the S pole 17E, the N pole17F or the like) of different polarity on the inner periphery-side ofthe magnet 11A. In this case, the first and second magnetic bodies 45Eand 46E guide the magnetic field lines from the two parts (for example,the N pole 16E and the S pole 17E) of the magnet 11A, which are locatedat different positions in the width direction (radial direction AD2) ofthe magnet 11A and have polarities different from each other, to thelength direction of the magnetosensitive member 47. Also in the electricsignal generation unit 31E, a magnetic circuit MC4 is formed from themagnet 11A so as to pass the first magnetic body 45E, themagnetosensitive member 47, and the second magnetic body 46E. Therefore,the magnetosensitive member 47 can effectively output the stable pulseby the reversal of the AC magnetic field due to the rotation of themagnet 11A, without being affected by the unnecessary magnetic field onthe side surface of the magnet 11A.

Third Embodiment

A third embodiment is described with reference to FIGS. 7A to 7C. Notethat in FIGS. 7A to 7C, the parts corresponding to FIGS. 6A to 6C aredenoted with the same reference signs, and the detailed descriptionsthereof are omitted. FIG. 7A is a plan view showing a magnet 11A and anelectric signal generation unit 31F of an encoder device in accordancewith the present embodiment, and FIG. 7B is a side view showing themagnet 11A shown in FIG. 7A, as a sectional view. In FIGS. 7A and 7B,the magnet 11A is configured so that the direction and strength of themagnetic field in the radial direction AD2 with respect to the rotaryshaft SF are changed by rotation.

In the present embodiment, the magnetosensitive member 47 of theelectric signal generation unit 31F is disposed in a space K so that thelength direction LD2 is orthogonal to the front surface of the magnet11A having a flat plate shape, in the vicinity of an inner surface ofthe magnet 11A having the space K inside. Also, the length direction LD2of the magnetosensitive member 47 in the electric signal generation unit31F is disposed to be orthogonal to the radial direction AD2 with beingspaced in a diametrical direction (for example, the radial direction) ofthe magnet 11A orthogonal to the rotary shaft SF or in a directionparallel to the diametrical direction. In the present embodiment, thelength direction LD2 of the magnetosensitive member 47 is substantiallyorthogonal to the radial direction AD2 that is the magnetizationdirection of the magnet 11A, and is also substantially parallel to theaxial direction of the rotary shaft SF. Also, a tip end portion of afirst magnetic body 45F on one end-side of the magnetosensitive member47 is disposed near an inner surface of a part of one polarity (forexample, the N pole 17F) on the inner periphery-side of the magnet 11A,and a tip end portion of a second magnetic body 46F on the otherend-side of the magnetosensitive member 47 is disposed near an innersurface of a part (for example, the S pole 17E) of the other polarity onthe inner periphery-side of the magnet 11A. In other words, the firstand second magnetic bodies 45F and 46F guide the magnetic field linesfrom the two parts (for example, the N pole 17F and the S pole 17E) ofthe magnet 11A, which are located at different positions in the θdirection and have polarities different from each other, to the lengthdirection LD2 of the magnetosensitive member 47. The otherconfigurations are similar to the first embodiment.

Also in the present embodiment, a magnetic circuit MC5 is formed fromthe magnet 11A so as to pass the first magnetic body 45F, themagnetosensitive member 47, and the second magnetic body 46F. Also, thelength direction of the magnetosensitive member 47 is disposed so as tobe substantially orthogonal to a tangential direction (herein, the θdirection) of the magnetic field line, which passes through asubstantial center in the length direction LD2 of the magnetosensitivemember 47, of the magnetic field lines generated on the inner surface ofthe magnet 11A. A magnetic field component unnecessary for pulsegeneration in the electric signal generation unit 31F including magneticfield lines generated on the inner surface of the magnet 11A isorthogonal to the length direction of the magnetosensitive member 47,and the unnecessary magnetic field component does not adversely affectthe generation of the magnetic domain wall from one end toward the otherend of the magnetosensitive member 47 caused by the reversal of the ACmagnetic field due to the rotation of the magnet 11A. For this reason,even when the magnetosensitive member 47 is disposed on the innersurface of the magnet 11A and the electric signal generation unit 31F isthus made small, it is possible to effectively generate the high-outputpulse (electric signal) by using the electric signal generation unit 31Fthrough the reversal of the AC magnetic field in the radial directionAD2 due to the rotation of the magnet 11A, without being affected by theunnecessary magnetic field component. The other effects are similar tothe above-described embodiments.

Note that in the present embodiment, like an electric signal generationunit of a modified embodiment shown in FIG. 7C, the magnetosensitivemember 47 may be disposed on an outer surface of the magnet 11A so thatthe length direction of the magnetosensitive member 47 is substantiallyperpendicular to the outer surface. In this case, a tip end portion of amagnetic body 45F1 on one end-side of the magnetosensitive member 47 isdisposed near a part (for example, the N pole 16E, the S pole 16F or thelike) of one polarity on the outer periphery-side of the magnet 11A, andthe other end of the magnetosensitive member 47 is disposed near a part(for example, the S pole 16F, the N pole 16E or the like) of differentpolarity on the outer periphery-side of the magnet 11A. In this case,one end of the magnetic body 45F1 is disposed near one end-side of themagnetosensitive member 47, and the other end of the magnetic body 45F1is disposed near the part of one polarity on the outer periphery-side ofthe magnet 11A. In other words, in the present modified embodiment, theother magnetic body (the first magnetic body or the second magneticbody) is omitted. In the present modified embodiment, the lengthdirection of the magnetosensitive member 47 is substantially parallel tothe radial direction that is the magnetization direction of the magnet11A, and is also substantially orthogonal to the θ direction(circumferential direction).

In the present modified embodiment, a magnetic circuit MC51 is formedfrom the magnet 11A so as to pass the magnetic body 45F1 and themagnetosensitive member 47. Therefore, the magnetosensitive member 47can effectively output the stable pulse by the reversal of the ACmagnetic field due to the rotation of the magnet 11A, without beingaffected by the unnecessary magnetic field on the side surface of themagnet 11A.

Fourth Embodiment

A fourth embodiment is described with reference to FIGS. 8A to 8E. Notethat in FIGS. 8A to 8E, the parts corresponding to FIGS. 3A to 3C aredenoted with the same reference signs, and the detailed descriptionsthereof are omitted.

FIG. 8A is a plan view showing a magnet 11 and an electric signalgeneration unit 31G of an encoder device in accordance with the presentembodiment, and FIGS. 8B and 8C are side views showing the magnet 11shown in FIG. 8A, as sectional views. In FIGS. 8A and 8B, the magnet 11is configured so that the direction and strength of the magnetic fieldin the axial direction AD1 parallel to the rotary shaft SF are changedby rotation. The magnet 11 has a plurality of polarities (for example,the N pole 16A and the S pole 16B) in the θ direction, and also hasparts (for example, the N pole 16A and the S pole 17A) of two polaritiesdifferent from each other in the thickness direction (radial directionAD2) orthogonal to the θ direction. The magnetization direction of themagnet 11 is the axial direction AD1.

In the present embodiment, the magnetosensitive member 47 of theelectric signal generation unit 31G is disposed so that the lengthdirection LD3 of the magnetosensitive member 47 is parallel to the frontsurface of the magnet 11 having a flat plate shape and the lengthdirection LD3 is perpendicular to the outer surface of the magnet 11, inthe vicinity of the outer surface of the magnet 11. Also, the lengthdirection LD3 of the magnetosensitive member 47 in the electric signalgeneration unit 31G is disposed to be orthogonal to the axial directionAD1 with being spaced in the diametrical direction (for example, theradial direction) of the magnet 11 orthogonal to the rotary shaft SF orin a direction parallel to the diametrical direction. In the presentembodiment, the length direction LD3 of the magnetosensitive member 47is substantially orthogonal to the axial direction AD1 that is themagnetization direction of the magnet 11, is substantially parallel tothe radial direction of the rotary shaft SF, and is substantiallyorthogonal to the θ direction (circumferential direction). Also, a tipend portion of a first magnetic body 45G on one end-side of themagnetosensitive member 47 is disposed near a part of one polarity (forexample, the N pole 16A) on the front surface-side of the magnet 11, anda tip end portion of a second magnetic body 46G on the other end-side ofthe magnetosensitive member 47 is disposed near a part (for example, theS pole 17A) of the other polarity on the back surface-side of the magnet11. In other words, the first and second magnetic bodies 45G and 46Gguide the magnetic field lines from the two parts (for example, the Npole 16A and the S pole 17A) of the magnet 11, which are located at sameangular position in the θ direction and have polarities different fromeach other, to the length direction LD3 of the magnetosensitive member47. The other configurations are similar to the first embodiment.

Also in the present embodiment, a magnetic circuit MC6 is formed fromthe magnet 11 so as to pass the first magnetic body 45G, themagnetosensitive member 47, and the second magnetic body 46G. Also, asshown in FIG. 8C, the length direction LD3 of the magnetosensitivemember 47 is disposed so as to be substantially orthogonal to atangential direction MD3 (herein, parallel to the axial direction AD1)of the magnetic field line MF3, which passes through a substantialcenter in the length direction LD3 of the magnetosensitive member 47, ofthe magnetic field lines generated on the side surface of the magnet 11.

A magnetic field component unnecessary for pulse generation in theelectric signal generation unit 31G including magnetic field linesgenerated on the side surface of the magnet 11 is orthogonal to thelength direction of the magnetosensitive member 47, and the unnecessarymagnetic field component does not adversely affect the generation of themagnetic domain wall from one end toward the other end of themagnetosensitive member 47 caused by the reversal of the AC magneticfield due to the rotation of the magnet 11. For this reason, even whenthe magnetosensitive member 47 is disposed near the magnet 11 and theelectric signal generation unit 31G is thus made small, it is possibleto effectively generate the high-output pulse (electric signal) by usingthe electric signal generation unit 31G through the reversal of the ACmagnetic field in the axial direction AD1 due to the rotation of themagnet 11, without being affected by the unnecessary magnetic fieldcomponent. The other effects are similar to the first embodiment.

Note that in the present embodiment, like an electric signal generationunit 31H of a modified embodiment shown in FIGS. 8D and 8E, a tip endportion of a first magnetic body 45H on one end-side of themagnetosensitive member 47 may be disposed near a part (for example, theN pole 16A, the S pole 16B or the like) of one polarity on the frontsurface-side of the magnet 11, and a tip end portion of a secondmagnetic body 46H on the other end-side of the magnetosensitive member47 may be disposed near a part (for example, the S pole 16D, the N pole16A or the like) of different polarity on the front surface-side of themagnet 11. In this case, the first and second magnetic bodies 45H and46H guide the magnetic field lines from the two parts of the magnet 11(for example, the N pole 16A and the S pole 16D), which are located atdifferent positions in the θ direction of the magnet 11 and havepolarities different from each other, to the length direction of themagnetosensitive member 47. Also in the electric signal generation unit31H, a magnetic circuit MC7 is formed from the magnet 11 so as to passthe first magnetic body 45H, the magnetosensitive member 47, and thesecond magnetic body 46H, and the magnetosensitive member 47 caneffectively output the stable pulse by the reversal of the AC magneticfield due to the rotation of the magnet 11, without being affected bythe unnecessary magnetic field on the side surface of the magnet 11.

Fifth Embodiment

A fifth embodiment is described with reference to FIGS. 9A and 9B. Notethat in FIGS. 9A and 9B, the parts corresponding to FIGS. 3A to 3C aredenoted with the same reference signs, and the detailed descriptionsthereof are omitted. FIG. 9A is a plan view showing a magnet 11B,magnetic sensors 51 and 52 (magnetism detection unit 12), and anelectric signal generation unit 31A of an encoder device in accordancewith the present embodiment, and FIG. 9B is a side view showing themagnet 11B of FIG. 9A, as a sectional view. In FIGS. 9A and 9B, themagnet 11B includes an annular magnet on the outer periphery-side wherean N pole 16G and an S pole 16H each having an opening angle of 180° anda fan shape are disposed in the rotating direction (θ direction) of therotary shaft SF and an annular magnet on the inner periphery-side wherean S pole 16J and an N pole 16I each having an opening angle of 180° anda fan shape are disposed in the θ direction. Also, on back surfaces ofthe N pole 16G and the S pole 16H on the outer periphery-side, an S pole17G and an N pole 17H having the same shape and different polarity arebonded, and on back surfaces of the N pole 16I and the S pole 16J on theinner periphery-side, an S pole 17I and an N pole 17J having the sameshape and different polarity are bonded. As such, phases of the annularmagnet on the outer periphery-side of the magnet 11B and the annularmagnet on the inner periphery-side are offset by 180°. Also, the magnet11B has two polarities different from each other in the thicknessdirection (axial direction AD1). In the magnet 11B, a boundary betweenthe S pole 16J and the N pole 16I on the inner periphery-sidesubstantially matches a boundary between the N pole 16G and the S pole16H on the outer periphery-side, with respect to the angular position inthe θ direction.

In the present embodiment, the magnetosensitive member 47 of theelectric signal generation unit 31A is disposed so that the lengthdirection of the magnetosensitive member 47 is parallel to the frontsurface of the magnet 11B having a flat plate shape and the lengthdirection is parallel to the rotating direction (θ direction) of therotary shaft SF, in the vicinity of the outer surface of the magnet 11B.Also, the tip end portion of the first magnetic body 45A on one end-sideof the magnetosensitive member 47 is disposed near a part of onepolarity (for example, the S pole 16H) on the front surface-side of themagnet 11B, and the tip end portion of the second magnetic body 46A onthe other end-side of the magnetosensitive member 47 is disposed near apart (for example, the N pole 17H) of the other polarity on the backsurface-side of the magnet 11B. In other words, the first and secondmagnetic bodies 45A and 46A guide the magnetic field lines from the twoparts (for example, the S pole 16H and the N pole 17H) of the magnet11B, which are located at same angular position in the θ direction andhave polarities different from each other, to the length direction ofthe magnetosensitive member 47.

Also, the magnetic sensors 51 and 52 are disposed so as to overlap aboundary part between the annular magnet on the inner periphery-side andthe annular magnet on the outer periphery-side, in the vicinity of thefront surface of the magnet 11B. An angle between the magnetic sensors51 and 52 is, for example, about 90°. The other configurations aresimilar to the first embodiment. In the present embodiment, themagnetization direction of the magnet 11B with respect to the electricsignal generation unit 31A is the axial direction AD1, and themagnetization direction with respect to the magnetic sensors 51 and 52is the radial direction. Also, the length direction of themagnetosensitive member 47 is substantially orthogonal to the axialdirection AD1 that is the magnetization direction of the magnet 11B, andis substantially parallel to the 0 direction (circumferentialdirection). Also in the present embodiment, the magnetic circuit MC1 isformed from the magnet 11B so as to pass the first magnetic body 45A,the magnetosensitive member 47, and the second magnetic body 46A. Also,the length direction of the magnetosensitive member 47 is disposed so asto be substantially orthogonal to a tangential direction (herein,parallel to the axial direction AD1) of the magnetic field line, whichpasses through a substantial center in the length direction of themagnetosensitive member 47, of the magnetic field lines generated on theside surface of the magnet 11B.

A magnetic field component unnecessary for pulse generation in theelectric signal generation unit 31A including magnetic field linesgenerated on the side surface of the magnet 11B is orthogonal to thelength direction of the magnetosensitive member 47, and the unnecessarymagnetic field component does not adversely affect the generation of themagnetic domain wall from one end toward the other end of themagnetosensitive member 47 caused by the reversal of the AC magneticfield due to the rotation of the magnet 11B. For this reason, even whenthe magnetosensitive member 47 is disposed near the magnet 11B and theelectric signal generation unit 31A is thus made small, it is possibleto effectively generate the high-output pulse (electric signal) by usingthe electric signal generation unit 31A through the reversal of the ACmagnetic field in the axial direction AD1 due to the rotation of themagnet 11B, without being affected by the unnecessary magnetic fieldcomponent. Also, each of the magnetic sensors 51 and 52 can detect achange in magnetic field including a magnetic field line MF4 that isgenerated between the annular magnet on the inner periphery-side of themagnet 11B and the annular magnet on the outer periphery-side. Theencoder device of the present embodiment can obtain the angle andmulti-turn information of the rotary shaft SF by using detection resultsof the magnetic sensors 51 and 52. The other effects are similar to thefirst embodiment.

Sixth Embodiment

A sixth embodiment is described with reference to FIGS. 10A and 10B.Note that in FIGS. 10A and 10B, the parts corresponding to FIGS. 9A and9B are denoted with the same reference signs, and the detaileddescriptions thereof are omitted.

FIG. 10A is a plan view showing a rotational disc 11D for opticalsensor, magnetic sensors 51 and 52, an optical sensor 21A, and anelectric signal generation unit 31A of an encoder device in accordancewith the present embodiment, and FIG. 10B is a side view showing amagnet 11B of FIG. 10A, as a sectional view. In FIGS. 10A and 10B, theannular rotational disc 11D (which is actually provided with an opening(not shown) through which the rotary shaft SF passes) is fixed to thefront surface of the magnet 11B. The rotational disc 11D and the magnet11B rotate in the 0 direction in conjunction with the rotary shaft SF.An incremental scale 11Da and an absolute scale 11Db are formedconcentrically on a front surface of the rotational disc 11D. Also, therotational disc 11D is disposed between the tip end portion of the firstmagnetic body 45A of the electric signal generation unit 31A and thefront surface of the magnet 11B. The magnetic circuit MC1 of theelectric signal generation unit 31A is formed to pass through therotational disc 11D.

Also, the optical sensor 21A includes a light-emitting element 21Aa thatgenerates illumination light, and light-receiving sensors 21Ab and 21Acthat receive the illumination light generated from the light-emittingelement 21Aa and reflected on the incremental scale 11Da and theabsolute scale 11Db. The encoder device of the present embodiment canobtain the rotating angle integrated each time the rotary shaft SFrotates by a predetermined angle from a predetermined reference angle,and an absolute angular position within one-turn of the rotary shaft SFby processing detection signals of the light-receiving sensors 21Ab and21Ac in a detection unit (not shown) similar to the detection unit 23 ofFIG. 1 . Also, it is possible to obtain the multi-turn information ofthe rotary shaft SF by performing one counting each time a relativeangular position exceeds 360°.

Similarly, the encoder device of the present embodiment can obtain therotating angle and multi-turn information of the rotary shaft SF byusing detection results of the magnetic sensors 51 and 52. Also, amagnetic field component unnecessary for pulse generation in theelectric signal generation unit 31A including magnetic field linesgenerated on the side surface of the magnet 11B is orthogonal to thelength direction of the magnetosensitive member 47, and the unnecessarymagnetic field component does not adversely affect the generation of themagnetic domain wall from one end toward the other end of themagnetosensitive member 47 caused by the reversal of the AC magneticfield due to the rotation of the magnet 11B. For this reason, even whenthe magnetosensitive member 47 is disposed near the magnet 11B and theelectric signal generation unit 31A is thus made small, it is possibleto effectively generate the high-output pulse (electric signal) by usingthe electric signal generation unit 31A through the reversal of the ACmagnetic field in the axial direction AD1 due to the rotation of themagnet 11B, without being affected by the unnecessary magnetic fieldcomponent. The other effects are similar to the first embodiment.

Note that when the plurality of electric signal generation units isprovided, like the embodiments and modified embodiments, the electricpower that is output from the electric signal generation unit 31A mayalso be used as a detection signal for detecting the multi-turninformation or may be used for supply to a detection system and thelike. Note that in the first embodiment, the magnet 11 is an eight-polemagnet having four poles in the circumferential direction and two polesin the thickness direction. However, the present invention is notlimited thereto, and can be changed as appropriate. For example, thenumber of poles of the magnet 11 in the circumferential direction may betwo or four or more.

Note that in the above embodiments, the position detection system 1detects the rotational position information of the rotary shaft SF(moving part), as the position information but may also detect at leastone of a position in a predetermined direction, a speed and anacceleration, as the position information. The encoder device EC maycomprises a rotary encoder or a linear encoder. Also, the encoder deviceEC may have a configuration where the electric power generation part andthe detection unit are provided on the rotary shaft SF and the magnet 11is provided outside the moving body (for example, the rotary shaft SF),so that the relative positions of the magnet and the detection unit arechanged with movement of the moving part. Also, the position detectionsystem 1 may not detect the multi-turn information of the rotary shaftSF, and may detect the multi-turn information by an external processingunit of the position detection system 1.

In the above embodiments, the electric signal generation units 31A and31B generate the electric power (electric signal) when a predeterminedpositional relation with the magnet 11 is satisfied. The positiondetection system 1 may also detect (count) the position information (forexample, the rotational position information including the multi-turninformation or the angular position information) of the moving part (forexample, the rotary shaft SF) by using, as the detection signal, thechange in electric power (signal) generated from the electric signalgeneration units 31A and 31B. For example, the electric signalgeneration units 31A and 31B may be used as sensors (position sensors),and the position detection system 1 may detect the position informationof the moving part by the electric signal generation units 31A and 31Band one or more sensors (for example, the magnetic sensor and thelight-receiving sensor). Also, when the number of the electric signalgeneration units is two or more, the position detection system 1 maydetect the position information by using the two or more electric signalgeneration units, as sensors. For example, the position detection system1 may detect the position information of the moving part by using thetwo or more electric signal generation units, as sensors, without usingthe magnetic sensors, or may detect the position information of themoving part without using the light-receiving sensor. Also, similarly tothe magnetic sensor, the position detection system 1 may determine therotating direction of the rotary shaft SF by using the two or moreelectric signal generation units, as sensors, based on two or moreelectric signals.

Also, the electric signal generation units 31A and 31B may supply atleast a part of electric power that is consumed in the positiondetection system 1. For example, the electric signal generation units31A and 31B may supply the electric power to a processing unit of theposition detection system 1, which has relatively small powerconsumption. Also, the electric power supply system 2 may not supply theelectric power to some of the position detection system 1. For example,the electric power supplying system 2 may intermittently supply theelectric power to the detection unit 13 and may not supply the electricpower to the storage unit 14. In this case, the electric power may besupplied intermittently or continuously to the storage unit 14 from apower supply, a battery and the like provided outside the electric powersupplying system 2. The electric power generation part may generate theelectric power by a phenomenon other than the large Barkhausen jump, andfor example, may not supply the electric power to the moving part (forexample, the rotary shaft SF) and some of the position detection system1. For example, the electric power supplying system 2 may intermittentlysupply the electric power to the detection unit 13 and may not supplythe electric power to the storage unit 14. In this case, the electricpower may be supplied intermittently or continuously to the storage unit14 from a power supply, a battery and the like provided outside theelectric power supplying system 2. The electric power generation partmay generate the electric power by a phenomenon other than the largeBarkhausen jump, and for example, may generate the electric power byelectromagnetic induction associated with the change in magnetic fielddue to movement of the moving part (for example, the rotary shaft SF).The storage unit in which the detection result of the detection unit isstored may be provided outside the position detection system 1 or may beprovided outside the encoder device EC.

[Drive Device]

An example of the drive device is described. FIG. 11 shows an example ofa drive device MTR. In descriptions below, the constitutional parts thatare the same as or equivalent to the above embodiments are denoted withthe same reference signs for omitting or simplifying the descriptions.The drive device MTR is a motor device including an electric motor. Thedrive device MTR comprises the rotary shaft SF, a main body part (drivepart) BD that rotates the rotary shaft SF, and the encoder device ECthat detects the rotational position information of the rotary shaft SF.

The rotary shaft SF has a load-side end portion SFa, and ananti-load-side end portion SFb. The load-side end portion SFa isconnected to another power transmission mechanism such as a decelerator.A scale S is fixed to the anti-load-side end portion SFb via a fixingpart. The scale S is fixed, and the encoder device EC is attached. Theencoder device EC is an encoder device in accordance with theembodiments, the modified embodiments or combinations thereof.

In the drive device MTR, the motor control unit MC shown in FIG. 1controls the main body part BD by using a detection result of theencoder device EC. Since the replacement of the battery of the encoderdevice EC is not required or is less required, the drive device MTR canreduce the maintenance cost. Note that the drive device MTR is notlimited to the motor device, and may also be another drive device havinga shaft part that rotates by using a hydraulic pressure or pneumaticpressure.

[Stage Device]

An example of a stage device is described. FIG. 12 shows a stage deviceSTG. The stage device STG has such a configuration that a rotationaltable (moving object) TB is attached to the load-side end portion SFa ofthe rotary shaft SF of the drive device MTR shown in FIG. 11 . Indescriptions below, the constitutional parts that are the same as orequivalent to the above embodiments are denoted with the same referencesigns for omitting or simplifying the descriptions.

In the stage device STG, when the drive device MTR is driven to rotatethe rotary shaft SF, the rotation is transmitted to the rotational tableTB. At this time, the encoder device EC detects the angular position ofthe rotary shaft SF, and the like. Therefore, it is possible to detectan angular position of the rotational table TB by using an output fromthe encoder device EC. Note that a decelerator and the like may bedisposed between the load-side end portion SFa of the drive device MTRand the rotational table TB. Since the replacement of the battery of theencoder device EC is not required or is less required, the stage deviceSTG can reduce the maintenance cost. Note that the stage device STG canbe applied to a rotational table provided in a machine tool such as alathe, for example.

[Robot Device]

An example of a robot device is described. FIG. 13 is a perspective viewshowing a robot device RBT. Note that FIG. 13 pictorially shows a part(joint part) of the robot device RBT. In descriptions below, theconstitutional parts that are the same as or equivalent to the aboveembodiments are denoted with the same reference signs for omitting orsimplifying the descriptions. The robot device RBT comprises a first armAR1, a second arm AR2, and a joint part JT. The first arm AR1 isconnected to the second arm AR2 via the joint part JT.

The first arm AR1 includes an arm part 101, a bearing 101 a, and abearing 101 b. The second arm AR2 includes an arm part 102 and aconnection part 102 a. The connection part 102 a is disposed between thebearing 101 a and the bearing 101 b at the joint part JT. The connectionpart 102 a is provided integrally with the rotary shaft SF2. The rotaryshaft SF2 is inserted into both the bearing 101 a and the bearing 101 bat the joint part JT. An end portion on a side of the rotary shaft SF2,which is inserted into the bearing 101 b, is connected to a deceleratorRG through the bearing 101 b.

The decelerator RG is connected to the drive device MTR, and deceleratesrotation of the drive device MTR to 1/100 or the like, for example, andtransmits the same to the rotary shaft SF2. Although not shown anddescribed in FIG. 13 , the load-side end portion SFa of the rotary shaftSF of the drive device MTR is connected to the decelerator RG. Also, thescale S of the encoder device EC is attached to the anti-load-side endportion SFb of the rotary shaft SF of the drive device MTR.

In the robot device RBT, when the drive device MTR is driven to rotatethe rotary shaft SF, the rotation is transmitted to the rotary shaft SF2via the decelerator RG. The connection part 102 a is integrally rotatedby the rotation of the rotary shaft SF2, so that the second arm AR2rotates with respect to the first arm AR1. At this time, the encoderdevice EC detects an angular position of the rotary shaft SF, and thelike. Therefore, it is possible to detect an angular position of thesecond arm AR2 by using an output from the encoder device EC.

Since the replacement of the battery of the encoder device EC is notrequired or is less required, the robot device RBT can reduce themaintenance cost. Note that the robot device RBT is not limited to theabove configuration, and the drive device MTR can be applied to avariety of robot devices having a joint.

What is claimed is:
 1. An encoder device comprising: a positiondetection unit for detecting position information of a moving part; amagnet having a plurality of polarities along a moving direction of themoving part; and an electric signal generation circuit generating anelectric signal, based on a magnetic characteristic of amagnetosensitive wire, the electric signal generation circuit having themagnetosensitive wire whose magnetic characteristic is changed by achange in magnetic field associated with relative movement to themagnet, wherein the magnetosensitive wire is disposed so that themagnetosensitive wire is spaced apart from a side surface of the magnetin a direction orthogonal to the moving direction and a length directionof the magnetosensitive wire is orthogonal to tangential directions ofat least some of magnetic field lines of the magnet.
 2. The encoderdevice according to claim 1, wherein the electric signal generationcircuit includes a magnetic body for guiding the magnetic field lines ofthe magnet in the length direction of the magnetosensitive wire.
 3. Theencoder device according to claim 1, wherein the length direction of themagnetosensitive wire is disposed so as to be substantially orthogonalto a tangential direction of a magnetic field line, which passes asubstantial center in the length direction of the magnetosensitive wire,of the magnetic field lines of the magnet.
 4. The encoder deviceaccording to claim 1, wherein the magnet has a flat plate shape alongthe moving direction, and has polarities different from each other in athickness direction orthogonal to the moving direction, and themagnetosensitive wire is disposed on a side surface of the magnet sothat the length direction is parallel to one surface of the magnethaving the flat plate shape.
 5. The encoder device according to claim 4,wherein the electric signal generation circuit includes a magnetic bodyfor guiding magnetic field lines from two parts of the magnet, which arelocated at the same position in the moving direction and have polaritiesdifferent from each other, to the length direction of themagnetosensitive wire.
 6. The encoder device according to claim 4,wherein the electric signal generation circuit includes a magnetic bodyfor guiding magnetic field lines from two parts of the magnet, which arelocated at different positions in the moving direction and havepolarities different from each other, to the length direction of themagnetosensitive wire.
 7. The encoder device according to claim 1,wherein the magnet has a flat plate shape along the moving direction,and has polarities different from each other in a width directionorthogonal to the moving direction, and the magnetosensitive wire isdisposed on a side surface of the magnet so that the length direction isorthogonal to one surface of the magnet having the flat plate shape. 8.The encoder device according to claim 7, wherein the electric signalgeneration circuit includes a magnetic body for guiding magnetic fieldlines from two parts of the magnet, which are located at differentpositions in the moving direction and have polarities different fromeach other, to the length direction of the magnetosensitive wire.
 9. Theencoder device according to claim 7, wherein the electric signalgeneration circuit includes a magnetic body for guiding magnetic fieldlines from two parts of the magnet, which are located at differentpositions in the width direction and have polarities different from eachother, to the length direction of the magnetosensitive wire.
 10. Theencoder device according to claim 1, wherein the magnet has a flat plateshape along the moving direction, and has polarities different from eachother in a width direction orthogonal to the moving direction, and themagnetosensitive wire is disposed on a side surface of the magnet sothat the length direction is parallel to one surface of the magnethaving the flat plate shape and is perpendicular to the side surface ofthe magnet.
 11. The encoder device according to claim 10, wherein theelectric signal generation circuit includes a magnetic body for guidingmagnetic field lines from a part of the magnet, which is located, in themoving direction, at a position different from a position at which themagnetosensitive wire is disposed, to the length direction of themagnetosensitive wire.
 12. The encoder device according to claim 1,wherein the magnet has a flat plate shape along the moving direction,and has polarities different from each other in a thickness directionorthogonal to the moving direction, and the magnetosensitive wire isdisposed on a side surface of the magnet so that the length direction isparallel to one surface of the magnet having the flat plate shape and isperpendicular to the side surface of the magnet.
 13. The encoder deviceaccording to claim 12, wherein the electric signal generation circuitincludes a magnetic body for guiding magnetic field lines from two partsof the magnet, which are located at the same position in the movingdirection, to the length direction of the magnetosensitive wire.
 14. Theencoder device according to claim 12, wherein the electric signalgeneration circuit includes a magnetic body for guiding magnetic fieldlines from two parts of one surface and other surface of the magnet,which are located at positions different from each other in the movingdirection, to the length direction of the magnetosensitive wire.
 15. Theencoder device according to claim 1, wherein the magnetosensitive wiregenerates large Barkhausen jump by a change in magnetic field associatedwith movement of the magnet.
 16. The encoder device according to claim1, wherein the electric signal generation circuit generates pulsedelectric power by movement of the moving part.
 17. The encoder deviceaccording to claim 1, further comprising a battery for supplying atleast a part of electric power that is consumed in the positiondetection unit, in accordance with an electric signal generated from theelectric signal generation circuit.
 18. The encoder device according toclaim 17, further comprising a switching unit for switching whether tosupply electric power from the battery to the position detection unit,in accordance with the electric signal generated from the electricsignal generation circuit.
 19. The encoder device according to claim 17,wherein the battery includes a primary battery or a secondary battery.20. The encoder device according to claim 17, wherein the positiondetection unit includes a magnet for detecting positions and a magnetismdetection unit, mutual relative positions of them being changed bymovement of the moving part, and detects the position information, basedon a magnetic field formed by the magnet for detecting positions, andthe magnetism detection unit detects the magnetic field formed by themagnet for detecting positions by using electric power supplied from thebattery.
 21. The encoder device according to claim 20, wherein themagnet for detecting positions also serves as the magnet that causes achange in magnetic field for the electric signal generation circuit togenerate an electric signal.
 22. The encoder device according to claim1, wherein the position detection unit includes: a scale that moves inconjunction with the moving part, an irradiation unit for irradiatingthe scale with light, and a light detection unit for detecting lightfrom the scale.
 23. The encoder device according to claim 1, wherein themoving part includes a rotary shaft, the magnet has a ring shape, andthe magnetosensitive wire is disposed outside of an outer surface orinside of an inner surface of the magnet.
 24. The encoder deviceaccording to claim 1, wherein the position detection unit includes: anangle detection unit for detecting angular position information withinone-turn of a rotary shaft, and a multi-turn information detection unitfor detecting, as the position information, multi-turn information ofthe rotary shaft.
 25. A drive device comprising: the encoder deviceaccording to claim 1; and a power supplying unit for supplying power tothe moving part.
 26. A stage device comprising: a moving object; and thedrive device according to claim 25 for moving the moving object.
 27. Arobot device comprising: the device according to claim 25; and an armfor causing relative movement by the drive device.